border-1px($color)
	position:relative;
	&:after{
		dispaly:block
		position:absolute;
		left:0;
		bottom:0;
		width:100%;
		border-top:1px solid $color;
		content:'';
	}
border-1px-top($color)
	&:before{
		dispaly:block
		position:absolute;
		left:0;
		top:0;
		width:100%;
		border-top:1px solid $color;
		content:'';
	}
bg-img(url)
	background-image: url(url+"@2x.png")
  @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3){
    background-image: url(url+"@3x.png")
  }
